This invention relates to a system to restrict ore rushes in ore pass shafts in underground mining.
Ore pass shafts are used where mining in ore bearing layers vertically spaced above a main drive shaft and comprising shafts through which the ore mined can be delivered to trucks or the like in the main drive shaft.
The ore pass shafts can be up to five meters in diameter and, on occasions, up to one thousand meters long.
The lower end of the ore pass shaft has a shute output with a gate thereon and, in practice, there may be a build up of ore of up to a depth of one hundred meters in the shaft.
As will be appreciated most mines have running water therein and it is not unusual for water to enter the pass shaft and as this water can effectively not escape from the shaft there can be substantial build up of water adjacent the base of the shaft.
This can lead to a situation that, when the gate is opened to permit ore to be delivered to a train, the ore and water can be uncontrollably released, partially because of the additional weight provided by the water but also because the ore is effectively lubricated by the water, and thus the ore leaves the gate much more rapidly than would otherwise be the case.
It is not unusual in such circumstances for the operators in the main drive shaft to be overwhelmed by the effluxion of ore and water and this can lead to fatalities amongst the operators.